In the packaging of integrated circuits, semiconductor dies may be stacked through bonding, and may be bonded to other package components such as interposers and package substrates. The resulting packages are known as Three-Dimensional Integrated Circuits (3DICs). The heat dissipation is a challenge in the 3DICs. There exists a bottleneck in efficiently dissipating the heat generated in the inner dies of the 3DICs. The heat generated in the inner dies has to be dissipated to outer components such as outer dies before the heat can be conducted to any heat spreader. Between the stacked dies, however, there exist other materials such as underfill, molding compound, etc, which are not effective in conducting heat. Furthermore, the stacked dies may also be molded in a molding compound, which prevents the efficient heat dissipation.
In a conventional package, a die stack including a plurality of dies may be stacked on a bottom die having a size larger than the die stack. The bottom die is further attached to a package substrate. A conformal metal lid is formed to cover the bottom die, and to encircle and cover the die stack. The conformal metal lid is attached to both the top surface of the edge portions of the logic die and the top surface of the die stack through Thermal Interface Materials (TIM). A heat sink is further attached to the top surface of the conformal metal lid through another TIM.